I. Field of the Invention
The present invention relates to gasification, and more particularly to a system and method for integrated gasification control.
II. Related Art
Gasification is among the cleanest and most efficient technologies for the production of power, chemicals and industrial gases from hydrocarbon feedstocks, such as coal, heavy oil, and petroleum coke. Simply stated, gasification converts hydrocarbon feedstocks into clean synthesis gas, or syngas, composed primarily of hydrogen (H.sub.2) and carbon monoxide (CO). In a gasification plant, the feedstock is mixed with oxygen (O.sub.2) and they are injected into a gasifier. Inside the gasifier, the feedstock and the O.sub.2 are subjected to a high-temperature and a high-pressure. As a result, the feedstock and the O.sub.2 break down into syngas.
In addition to H.sub.2 and CO, the syngas contains other gases in small quantities, such as ammonia, methane and hydrogen sulfide (H.sub.2 S). As much as 99% or more of the H.sub.2 S present in the syngas can be recovered and converted to elemental sulfur form and used in the fertilizer or chemical industry. Ash and any metals are removed in a slag-like state, and the syngas is cleansed of particulates. The clean syngas is then used for generating electricity and producing industrial chemicals and gases.
Gasification allows refineries to self-generate power and produce additional products. Thus, gasification offers greater efficiencies, energy savings, and a cleaner environment. For example, a gasification plant at a refinery in El Dorado, Kans. converts petroleum coke and refinery wastes into electricity and steam, making the refinery entirely self-sufficient for its energy needs and significantly reducing waste and coke handling costs. For these reasons, gasification has increasingly become popular among refiners worldwide. Currently, there are several hundred gasification plants in operation worldwide.
The operation of the gasification plant requires various control systems to control the gasifier and other equipments connected thereto. Currently, gasification plants utilize independent controllers, for example, proportional integral derivative (PID) controllers, to independently control various processes in the gasification plant. The independent controllers operate separately and do not interact with each other. As a consequence, the desired setpoint at each controller must be entered separately. Unfortunately, independent controllers often provide poor response, which results in increased wear and tear of the gasifier and other associated equipments. Specifically, poor controller response can damage a gasifier refractory vessel (a layer of bricks in the gasifier designed to keep heat inside the gasifier) and thermocouple temperature sensors that measure the temperatures in the gasifier. Poor controller response also leads to gasifier shut downs and "off-spec" syngas that does not meet required specifications.
For these reasons, a need has been recognized for an integrated control system that will control various critical components of the gasification plant. An integrated control system should improve the reliability of the gasification plant by reducing gasifier shut downs and maximizing run-time. Also, an integrated control system should reduce wear and tear of the gasifier and other associated components.